Generally, it is desired that a coating system for coating a work piece such as the body of an automobile should be able to reduce the amount of paint discarded at the time of color change and should be able to cope with numerous coating colors. As a coating system for coping with this, a cartridge type coating system is known which is arranged such that a paint cartridge with a paint of each color filled therein is interchangeably mounted on a coating apparatus which is a paint spraying means.
The paint cartridge used in this cartridge type coating system is largely constituted by a tank accommodating cylindrical body formed of a transparent or translucent hollow tubular body whose front side in the front and rear directions is mounted to the coating apparatus and by a baggy tank which is provided in that tank accommodating cylindrical body, has its interior formed as a paint chamber for the efflux and influx of a paint to supply the paint to the coating apparatus, and has its exterior between the same and the tank accommodating cylindrical body formed as an extruding liquid chamber for the efflux and influx of an extruding liquid for extruding the paint in the paint chamber.
Here, since the baggy tank is formed by a bag constituted of a flexible resin material, the baggy tank has a possibility of breaking and forming a hole due to aged deterioration and the like. If coating is continued with the hole formed in the baggy tank, the paint and the extruding liquid become mixed and disadvantageously cause a deterioration in the coating quality.
Accordingly, the paint cartridge is arranged such that the baggy tank is formed in a dual structure constituted by an inner bag and an outer bag, and an atmosphere passage for making the space between the inner bag and the outer bag open to the atmosphere is provided in the tank accommodating cylindrical body. Consequently, in the event that the inner bag or the outer bag of the baggy tank has broken and a hole has been formed, the paint or the extruding liquid is discharged through the space between the inner bag and the outer bag to the outside via the atmosphere passage, thereby making it possible to notify the breakage of the inner bag or the outer bag (for example, Patent Documents 1, 2, 3, and 4).